单项选择题

A．Use of copper conductors.
B．Use of plastic insulator (绝缘体).
C．Use of silicon (硅) semiconductors.
D．Elimination of chemicals.
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A．Chinese.B．Mexican.C．Italian.D．Spanish.
A．Chinese.
B．Mexican.
C．Italian.
D．Spanish.
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A．The weather for tomorrow.B．The climate in cold countries. C) The changes in weather.C．The cold winter.
A．The weather for tomorrow.
B．The climate in cold countries. C) The changes in weather.
C．The cold winter.
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